The purpose of this study is to understand dynamic characteristics of the sitting human body by performing multi-dimensional experiments, and to make up a three-dimensional dynamic model of the human body. Firstly vibrational experiments are performed by using a three-directional shaking table on which a wooden seat is installed. Experimental subjects sitting on the seat are excited with respect to three directions, i.e., fore-and-aft (x-axis), lateral (y-axis), vertical (z-axis) one after another. Paying attention to the head, vibrational characteristics of the sitting human body are clarified by transmissibilities between the seat's acceleration and the acceleration of the head with respect to three translational directions, i.e., 3x3=9 transmissibilites are measured. As a result, the head's motion has two dominant resonant peaks up to 20Hz in each translational directions, and the fore-and-aft motion and the vertical motion is coupled. It is supposed that the coupling is caused by t
… Morehe rotational motion of the head around y-axis (piching). Secondly a three-dimensional dynamic model of the human body is built up considering the experimental results. In the model, the body and the head are regarded as rigid bodies and they are connected to each other by the translational springs and dampers. The body is able to move in three translational directions, and the head is able to move in the vertical direction and in two rotational directions relatively to the body. The model has six dof's in total. Through the comparison of transmissibilities obtained by the experiment and those synthesized from the model, it is confirmed that the model reflects the fundamental dynamic properties of sitting human body.(1)頭部の回転振動について加振方向は,水平前後(x),左右(y),垂直(z)の3方向であるが,x,z方向間において,入出力の連成を生ずるモードが確認されていたが,この連成モードは,頭部のピッチ振動が関与していることが,実験により確かめられた.すなわち,連成のある共振周波数においては,頭部のピッチ振動も卓越していた.また,従来不明確であった,ピッチ振動の位相も伝達関数の測定により明らかになった.(2)胴体部の並進振動について動特性モデルにおいては,頭部と胴体部をそれぞれ剛体と考え,これらを,バネ,ダッシュポットで結合して構成している.そこで,胸部の測定データを胴体部の並進振動成分とみなし,モデルを構築する際に参照した.振動モードによっては,胴体部においてもx-z方向間の連成が認められた.これは,動特性モデルでは反映されなかった点であり,今後の課題と考える.(3)動特性の入力依存性について人体の動特性は,様々な不確定要因があり,非線形要素も存在している.本研究では,動特性モデルの適用範囲を検討するために,人体の伝達関数の入力依存法を検討した.加振波形は,ランダム波として,入力レベルを0.05〜0.35G(rms)の範囲で変化させ,得られた伝達関数の入力依存性を調べた.その結果,入力レベルが増加するとともに,伝達関数のゲインが減少するという傾向が明らかになった. Less